The invention relates to fish farming systems and effluent, waste or water treatment systems which are generically referred to as aquaculture systems in this specification.
Conventional fish farm production systems are of two main types, namely a pond based system or a cage/raceway production system.
In pond production fish are stocked in growing ponds. Three regimes exist:
(a) Fish are left to survive on the plant and animal life of the pond (typical yield 200 kg/hectare)
(b) The ponds are fertilised (typical yield 1-2 ton/hectare)
(c) Ponds are fertilised and the fish are also fed high grade food (yield 3-10 ton/hectare)
This type of fish farming is a batch process. Eventually the pond water becomes unsuitable for fish production and has to be replaced, either naturally (rain, etc) or by mechanical means. Generally the best yields achievable are 1 kg of fish per ton of water.
In cage fish farming, fish are held in cages floating in a large body of water (lake or sea) and the fish are fed complete diets. Fish waste drops through the meshes of the cages. This technique relies on the large body of water to dilute the water in the cages and so maintain suitable growing conditions. Yields based on cage area can be quite large, 100 tons per hectare. However, based on total water requirements yields are only of the order of one ton per hectare.
In raceway systems fish are housed in raceways and are fed complete diets. Fresh water is continuously passed through the raceway to remove waste and to maintain suitable growing conditions. Yields based on the area of raceway, can be up to 400 tons per hectare, however, based on water requirements (60 cubic meters of water per hour, per ton of fish) yields are of the order of 1 ton of fish per 0.5 million cubic meters of water.
In some raceway systems, wastewater is treated and recirculated. Treatment involves passing the water through aerobic digesters (sometimes called xe2x80x9cactive filtersxe2x80x9d) and reoxygenation. This treatment is sufficient to reduce ammonia and nitrites to less toxic nitrates, but eventually the water becomes unsuitable for fish growing and has to be replaced. Biomass also builds up in the aerobic digesters. In the last few years there has been an increasing interest in using plants as a means of water treatment (the new fields of aquaponics). In this technique, the plants, e.g. tomatoes, lettuce, etc are grown hydroponically with wastewater from the fish being used as the hydroponic solution. The treated water from the hydroponic bed is then recycled to the fish containers. Some of the hydroponic plants are also used as a food supplement for the fish. Aquaponics is still an infant science and is not widely applied.
This invention is directed towards providing an aquaculture system which will overcome at least some of the problems with conventional systems.
According to the invention there is provided an aquaculture apparatus comprising an elongate tube of flexible translucent material, the tube extending longitudinally along a tube site and having a lower section defining a water course. Preferably the tube is gas, especially air supported.
In a preferred embodiment the apparatus includes inflation means for inflating the tube and/or for maintaining the tube inflated. The inflation means is preferably an air handling means, especially a fan which is particularly suitable in a configuration in which the apparatus includes an access means. Alternatively the air handling means is a compressor which may deliver air through the water.
In a preferred embodiment the air handling means comprises a wind directing system for directing wind into the tube to inflate the tube and/or to maintain the tube inflated.
Preferably the apparatus includes access means for access to the tube. The access means may comprise an access door.
In a preferred embodiment the apparatus includes retaining means for retaining the tube in a desired position on a site. Preferably the retaining means extends longitudinally external of the tube. The retaining means may be a mound engaging the tube.
In a preferred arrangement there are a number of tubes which are arranged substantially parallel in generally side by side relation.
Preferably fluid connection means is provided between the tubes. The fluid connection means typically comprises a water-carrying channel means.
Preferably water flow control means are provided between the tubes. The water flow control means may include a weir means.
Ideally the or each tube is of plastics material.
Preferably each tube is for example of polyvinyl chloride or polyethelene. The material preferably comprises a number of layers. The material is preferably at least 100 microns thick and may be about 200 microns thick.
In a preferred embodiment the tube, in the expanded configuration has a diameter of at least 5000 mm, ideally a diameter of at least 6000 mm.
The or each tube is preferably at least 50 m long.
In a particularly preferred embodiment of the invention the apparatus includes a cover extending externally over the tube. The cover may be translucent or in very hot climates may form a shade.
Preferably the cover is at least partially spaced apart from the tube. A spacing between the outer cover and the tube preferably contains air. Indeed, the cover may be air supported.
In one embodiment the cover is of similar material to that of the tube.
The apparatus preferably includes cover retaining means for retaining the cover in position over the tube. Preferably the cover retaining means extends longitudinally of the cover and tube. The cover retaining means preferably also extends transversely of the cover and the tube. The cover retaining means may comprise a mound of clay or the like.
The apparatus may be adapted for rearing fish and/or for effluent and/or water treatment and/or for growing aquatic plants and/or for growing fish food.
The apparatus may define various modules of a fish rearing, effluent treatment, water treatment, aquatic plants, and/or fish food systems. For example the apparatus may form a digester module, a zooplankton module, higher order aquatic plants module, a dry matter content consuming module, and/or a fish rearing module.
The invention also provides an aquaculture system comprising a number of tubes as defined in the invention, the tubes defining at least some of the modules of an integrated system.
The aquaculture system preferably comprises:
an aerobic digester for digesting waste and producing biomass;
a primary algae treatment section for treating the biomass from the aerobic digester;
a zooplankton module for consuming the algae treated biomass and generating zooplankton and water;
an algae module for treating the water from the zooplankton module; and
a dry matter content consuming section for consuming at least some of the zooplankton harvested from the zooplankton module.
In a preferred embodiment of the invention the aerobic digester and primary algae treatment section are provided in the same module.
In one embodiment of the invention the dry matter content consuming section is a fish rearing module.
In this case, preferably waste generated in the fish rearing module is digested in the aerobic digester.
In another aspect the invention provides an aquaculture apparatus comprising a plurality of tubes as defined in the invention, the tubes defining at least some of the modules of a fish rearing system.
In one embodiment the apparatus comprises:
a fish rearing module;
a digester module for treating by-products from the fish rearing module;
a zooplankton module for consuming biomass produced by the digester, the zooplankton module producing zooplankton and water; and
an algae production module;
In this case the zooplankton module may be for producing carnivorous zooplankton.
Preferably the apparatus includes:
a herbivorous zooplankton module for consuming algae produced in the algae production unit; and
a higher order plant module for consuming waste produced by the herbivorous zooplankton module.
Ideally carnivorous zooplankton from the carnivorous zooplankton module provide food which is fed to the fish in the fish rearing module.
Preferably herbivorous zooplankton from the herbivorous zooplankton module provide food which is fed to fish in the fish rearing module.
In one arrangement higher order plants produced in the higher order plant module provide food which is fed to fish in the fish rearing module.
Purified water produced in the higher order plant module preferably provides a water supply to the fish rearing module.
In a particularly preferred embodiment at least some of the modules are defined by an elongate tube of flexible translucent material, the tube extending longitudinally along a tube site and having a lower section defining a water course.
In a further aspect the invention provides an aquaculture system comprising:
an aerobic digester for digesting waste and producing biomass;
a primary algae treatment section for treating the biomass from the aerobic digester;
a zooplankton module for consuming the algae treated biomass and generating zooplankton and water;
an algae module for treating the water from the zooplankton module; and
a dry matter content consuming section for consuming at least some of the zooplankton harvested from the zooplankton module.
Preferably the aerobic digester and primary algae treatment section are provided in the same module.
In one embodiment the dry matter content consuming section is a fish rearing module. In his case preferably waste generated in the fish rearing module is digested in the aerobic digester.
In another aspect the invention provides an aquaculture system comprising:
a fish rearing module;
a digester module for treating by-products from the fish rearing module;
a zooplankton module for consuming biomass produced by the digester, the zooplankton module producing zooplankton and water; and
an algae production module.
The zooplankton module may produce carnivorous zooplankton.
Preferably the aquaculture system includes:
a herbivorous zooplankton module for consuming algae produced in the algae production unit; and
a higher order plant module for consuming waste produced by the herbivorous zooplankton module.
Carnivorous zooplankton from the carnivorous zooplankton module preferably provide food which is fed to the fish in the fish rearing module.
Herbivorous zooplankton from the herbivorous zooplankton module preferably provide food which is fed to fish in the fish rearing module.
Higher order plants produced in the higher order plant module preferably provide food which is fed to fish in the fish rearing module.
Purified water produced in the higher order plant module preferably provides a water supply to the fish rearing module.
In a particularly preferred embodiment at least some of the modules are defined by an elongate tube of flexible translucent material, the tube extending longitudinally along a tube site and having a lower section defining a water course.